Low-frequency spontaneous radiation in a free-electron laser in the trapped regime

The electromagnetic radiation generated by ultra-relativistic positrons channeling in a crystalline undulator is discussed. The crystalline undulator is a crystal whose planes are bent periodically with the amplitude much larger than the interplanar spacing. Various conditions and criteria to be fulfilled for the crystalline undulator operation are established. Different methods of crystal bending are described. We present the results of numeric calculations of spectral distributions of the spontaneous radiation emitted in the crystalline undulator and discuss the possibility to create the stimulated emission in such a system in analogy with the free electron laser. A careful literature survey covering the formulation of all essential ideas in this field is given. Our investigation shows that the proposed mechanism provides an efficient source for high energy photons, which is worth studying experimentally.

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A Free Electron Laser–Photoemission Electron Microscope System (FEL–PEEM)

Surface Review and Letters ◽

10.1142/s0218625x98001596 ◽

1998 ◽

Vol 05 (06) ◽

pp. 1257-1268 ◽

Cited By ~ 53

Author(s):

H. Ade ◽

W. Yang ◽

S. L. English ◽

J. Hartman ◽

R. F. Davis ◽

...

Keyword(s):

Electron Microscope ◽

Energy Range ◽

Photon Energy ◽

Free Electron ◽

Free Electron Laser ◽

Spontaneous Radiation ◽

Laser Photoemission ◽

Emission Mode ◽

First Results ◽

Photoemission Electron

We report first results from our effort to couple a high resolution photoemission electron microscope (PEEM) to the OK-4 ultraviolet free electron laser at Duke University (OK-4/Duke UV FEL). The OK-4/Duke UV FEL is a high intensity source of tunable monochromatic photons in the 3–10 eV energy range. This tunability is unique and allows us to operate near the photoemission threshold of any samples and thus maximize sample contrast while keeping chromatic berrations in the PEEM minimal. We have recorded first images from a variety of samples using spontaneous radiation from the OK-4/ Duke UV FEL in the photon energy range of 4.0–6.5 eV. Due to different photothreshold emission from different sample areas, emission from these areas could be turned on (or off) selectively. We have also observed relative intensity reversal with changes in photon energy which are interpreted as density-of-state contrast. Usable image quality has been achieved, even though the output power of the FEL in spontaneous emission mode was several orders of magnitude lower than the anticipated full laser power. The PEEM has achieved a spatial resolution of 12 nm.

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Main-signal filamentation in free-electron lasers with deeply trapped particles

Journal of Plasma Physics ◽

10.1017/s0022377800014999 ◽

1990 ◽

Vol 44 (1) ◽

pp. 33-45 ◽

Cited By ~ 4

Author(s):

F. B. Rizzato

Keyword(s):

Electric Fields ◽

Free Electron ◽

Free Electron Laser ◽

Electromagnetic Waves ◽

Transverse Electric ◽

Low Frequency ◽

Fast Wave ◽

Free Electron Lasers ◽

Trapped Particles ◽

Transverse Electric Fields

The filamentation of electromagnetic waves in a free-electron laser with deeply trapped electrons is analysed. This instability is the result of particle bunching along transverse directions (with respect to the fast wave vector), as opposed to the untrapped-electron case, where it is a result of longitudinal bunching. Two cases are considered: (i) the non-resonant or reactive one, with purely imaginary growth rates; and (ii) the resonant one, with large (small) values of the real (imaginary) part of the perturbing frequency. In particular, we find that the reactive instability occurs only when the wiggler amplitude is unusually large. On the other hand, we show that the resonant process (with frequencies close to the synchrotron frequency) may be relevant for conventional free-electron lasers and that the growth rate for quasi-trans verse perturbations may be larger than that corresponding to longitudinal perturbations. Owing to the inhomogeneity and anisotropy of our system, low-frequency magnetic fields are generated. These fields, as well as the transverse electric fields, are analysed, and their role in the low-frequency dynamics is clarified.

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A helium nanodroplet setup for mid and far-infrared spectroscopy using pulsed-free-electron lasers: vibrational spectra of propargyl alcohol

RSC Advances ◽

10.1039/c7ra08102b ◽

2017 ◽

Vol 7 (86) ◽

pp. 54318-54325 ◽

Cited By ~ 7

Author(s):

Devendra Mani ◽

Theo Fischer ◽

Raffael Schwan ◽

Arghya Dey ◽

Britta Redlich ◽

...

Keyword(s):

Infrared Spectroscopy ◽

Free Electron ◽

Free Electron Laser ◽

Low Frequency ◽

Far Infrared ◽

Molecular Clusters ◽

Free Electron Lasers ◽

Far Infrared Spectroscopy ◽

Molecular Motions ◽

Helium Nanodroplets

Helium nanodroplets spectroscopy in combination with free electron laser. The combination is suitable for studying molecular clusters in 66–3600 cm−1 spectral range, covering the important low-frequency large amplitude intra and inter-molecular motions.

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